Apparatus for centrifugal casting of pipe



V. A. SZWED APPARATUS FOR CENTRIFUGAL CASTING 0F PIPE July 5; 1960 4 Sheets-Sheet 1 Filed June 1, 1959 VmTOR A. .S zwao July 5, 1960 v. A. SZVWAED 9 3, 9

APPARATUS FOR CENTRIFUGAL CASTING OF PIPE Filed June 1, 1959 4 Sheets-Sheet 2 NR OPERATE 3-WAY VALVE l8 SOLENOID OP- AMPLIFIER T ERATED B-WAY AIR PILOT VAL I I mszcowo TIMER 39 SUPPLY FIG .4

I INVENTOR. \ficroz A. Sauce I July 5, 1960 v. A. SZWED 2,943,369

APPARATUS FOR CENTRIFUGAL CASTING 0F PIPE Filed June 1, 1959 4 Sheets-Sheet 3 INVENTOR.

l/lc'roz A. Szweo July 5, 1960 v. A. SZWED 2,943,369

APPARATUS FOR CENTRIFUGAL CASTING 0F PIPE Filed June 1, 1959 4 Sheets-Sheet 4 j PHOTOELECTRIC A c SUPPLY CELL SHUTTER A.c. y FIRST I SUPPLY TIMER I i LADLE DRIVE x 39 cIRcuII' SECOND AMPLIFIER TIMER A .c. SUPPLY SUPP TO PILOT VALVE OF HYDRAULIC S S FlG.6

INVENTOR.

14 01 A. Say/so Patented July 5, 1960 APPARATUS FOR CENTRIFUGAL CASTING OF PIPE Victor A. Szwed, Burlington, N.J., assignmto United States Pipe and Foundry Company, Birmingham, Ala., a corporation of New Jersey Filed June 1, 1959, Ser. No. 817,202 4 Claims. (Cl. 2265) The present invention relates to the manufacture of tubular metal castings, and more particularly is concerned with improvements in the apparatus used in manufacture of cast iron pipe by the De Lavaud process.

The De Lavaud process of casting pipe in permanent metal molds has been extensively practiced in this country for many years. Present methods comprise the use of cylindrical metal molds mounted on rollers in a water jacket and adapted to be rotated at suitable speeds. The water jacket is mounted on wheels so that the entire assembly can be moved by means of a hydraulic cylinder in the direction of the longitudinal axis of the mold. This movement is along a fixed bed inclined slightly from the horizontal. The molten metal is fed into the mold through a similarly inclined trough which is mounted at the upper end of the fixed bed and extends like a cantilever beam almost the full length of the mold when it is at the extreme upper position. When the mold is in this position, it is ready for casting. After the casting machine ladle has been filled, the machine operator brings the mold up to speed and actuates the mechanism controlling the tilting of theladle. In a few seconds the iron has filled the bell space at which time the operator starts the mold carriage longitudinally down the inclined bed. The stream of iron discharged from the trough is distributed along the surface of the mold where it is held in place by centrifugal force and forms the pipe upon cooling. After the metal has solidified, mold rotation is stopped and the pipe is extracted from the mold by moving the mold carriage longitudinally up the inclined bed while holding the pipe stationary. The mold carriage is then moved back down the inclined bed to place the mold in a convenient position for setting the bell core, and if a mold coating is used, it may be applied during this stroke of the machine. The bell core is then set and the mold carriage moved to the extreme upper end of the inclined bed to begin another casting cycle.

The distribution of the metal along the mold length is controlled by the operator who must start the machine retracting from the trough at the correct moment or else the metal delivered to the bell end will not give the proper bell end thickness. For instance, if the carriage movement is started too soon the hell end will be too thin and if it is started late the bell end will be thick. Since it is usually impractical to place the machine operator in a position which commands a good view of the bell end of the mold, it is usually necessary to have the bell core setter, who is in a position which aifords the best view of the bell end of the mold, signal the operator to start the mold carriage retracting from the trough. This is called flagging and is accomplished by throwing asWitch which turns on a light or other suitable signal on the operators panel.

In addition to starting the mold attraction at the proper instant, the operator must also judge the proper position in which to stop the mold carriage momentarily while the spigot end of the pipe is being cast, after which retraction, of the mold carriage is completed, and the ladle pour is stopped. This is known as hand-checking and 1s necessary to build up the proper metal thickness at the spigot. end of the mold. It is apparent that it is completely within the control of the operator who determines both the position and time stopped. When the mold movement is stopped in the wrong position or for' too short a time, the spigot end is made thin, and if it is stopped for too long a time the spigot end is cast thick.

From the above it is obvious that the quality of the pipe cast depends to a large measure on the skill and judgment of the casting crew operating the machine. With the human element involved in flagging the machine, the possibility of casting consecutive pipe with the same thickness at the bell is remote, and in practice the metal thickness at the bell varies considerably. Again, during the hand-check, the carriage position and the time the carriage is stopped are dependent upon the judgment of the operator and for this reason the metal thickness of the spigot end varies from pipe to pipe. Since the period of time during which the ladle is tilting in pouring position depends upon both the time which elapses before the machine is flagged and the period of time in which the machine is stopped during the hand-checking, the total amount of metal poured will vary from pipe to pipe so that not only are pipe non-uniform in thickness from part to part of the same pipe, but they are also nonuniform in thickness and weight from one pipe to another.

Accordingly, the object of this invention is the provision of a procedure wherein improved uniformity in pipe thickness and weight is obtained.

A further object of this invention is the provision of a casting machine for casting pipe which requires a minimum of human judgment to operate.

A still further object of this invention is the provision of a casting machine with automatic flagging means.

Another object of the invention is the provision of a casting machine with automatic hand-checking means capable of slowing down the machine movement at a set position for a set time.

Another object of the invention is the provision of a casting machine with means for actuating ladle dump reversal after a set time to cut off metal flow.

An important object of the invention is the provision of an apparatus incorporating all the features named above.

Other objects and advantages of the present invention will be apparent to those skilled in the art from the following description taken in conjunction with the drawings in which:

Figure 1 shows a De Lavaud casting machine modified in accordance with this invention at the start of the vcasting stroke.

Figure 2 shows a De Lavaud casting machine modified in accordance with this invention near the end of the casting stroke.

Figure 3 shows a De Lavaud casting machine modivfied in accordance with this invention in the end posiv semi-automatically in such a manner as to minimize human judgment thereby obtaining pipe of more uniform thickness and weight. The principal features of the invention are automatic flagging, handchecking and ladle cut back which are the three areas in which the human element plays such an important part in the control of pipe thickness and weight.

Referring nowto Figures 1-3 which show a casting machine in various positions of the casting stroke, the general structure of the machine is seen to comprise a mold carriage l which is adapted to move up and down an inclined bed2. At'the upper extreme of the inclined bed the machine casting ladle 3 is mounted so-tliat it maybe pivoted about trunnions 4 by hydraulic cylinder 5. 'I'hemachine ladle 3 is adapted, to-empty into trough 6 which is firmly mounted on base 7 and extends substantially parallel to the inclined bed: for about thelength of the mold 8:which is mounted'in'mold carriage llwith its spigot end 9 toward the machine ladle 3. Theopposite endof the mold is adapted to'receive abell core -10, 'and the mold is mounted so that it may be rotated about" its longitudinal axis by' electric motor 11. Along the side of the mold carriage there is provided. a shoe 12 whichis positioned in line with lst.limit-switch.13- and 2nd limit switch 14 so that it will depress theswitches during'the retraction of the mold carriage. If desiredseparate-limit switches-13 and 14 may be replaced with asingle double acting limit switch. At the lowerendofthe inclined'bed a'bumping block 15' is provided, and to the rear of the bumpingblock a photoelectric cell 16 in anaimingtube is mounted so as to aim at the extreme lower end 1-7 of the trough. The photoelectric cell-16 ismounted on an amplifier containing box 18 which is also-providedwith a shield or shutter 19 which can be raised or loweredby. electrical means to provide a shield for the photoelectric cell after it has served its function in the casting cycle.

The block diagram in Figure 4 shows the automatic flagging mechanism. The photoelectric cell 20v which. is aimed at the end of the casting machine pouring trough, detects the flow of molten metal from the. end of the trough. The signal is amplified by amplifier18. to provide a signal for actuating the second timer shown-in Figure 6 and to actuate the solenoid operated. 3-way pilot valve. 20 which in turn controls the flow of air in the pneumatic circuit composed of two 3-way air operated valves 21 and 22 and a pneumatic cylinder 23 which is connected to machine operating lever 24 which actuates a 4-way valve 25 in the casting machine hydraulic system (also shown in Figure The operation of the machine operating lever retracts the mold carriage from the pouring spout.

The 4-way valve 25 is also shown in Figure 5 which is a block. diagram of the mold carriagehydraulic system. The 4-way operating valve 25 provides .for movement of the machine travel hydraulic cylinder 28 in either direction and the fluid supply may be cut off by gate. valve. 26. When the machine is in a non-casting portion of the casting cycle, by-pass valve 27 is opened by the operator to provide for rapid movement of the mold carriage. At the beginning of the casting stroke by-pass valve 27 is closed so that fluid flow in the hydraulic system is controlled by adjustable valve 29 which has been adjusted to provide the proper casting machine traverse rate. Reduction of the traverse speed isaccomplished by closing air operated valve 30 so that fluid flow in the hydraulic system is controlled by needle valve 31 which hasbeen set for a predetermined fluid flow rate. The opening and closing of air operated hydraulic valve 30 is controlled by solenoid operated air pilot valve 32' which is controlled, in turn, by timer 33. The actuation of the timer 33 is accomplished by the closing of the second limit switch 14 atthe correct instant by the shoe 12 on the side of the mold carriage. Slow down, which is necessary for handchecking or casting of the spigot, is maintained for the time pre-set on timer 33.

The block diagram in Figure 6 represents the electrical circuits which accomplish automatic cut back of the ladle 1 When molten metal reaches the end of the trough, the photoelectric cell 16 detects it. The signal from the photoelectric cell 16 is sent toamplifier 18 which provides signal to the solenoid operated pilot valve 20 (shown in Fig. 4) and actuates second timer 39 which is set for a predetermined time necessary to pour enough metal-for. the pipe being cast. The second timer 39 is connected in parallel with the first timer 36 so that upon the expiration of the time set on the first timer the second timer will continue to provide power to thejladle drive circuit; The time for which first timer 36 is set'is not precise and any setting which will run out after the second timer is energized but before it de-energizes is satisfactory. At the end of the predetermined time set on the second timer power to the ladle pour circuit 38 is cut OE and the ladle reverses cutting off the metal pour. This scheme provides for pouring only for a fixed time after molten metal reaches the bell end of the trough, so that if the pour rateis. constant the amount of metal poured will be known.

Referring now to Figures 1-6, a description of an operating cycle of the casting machine will be given; At the end of a previous casting cycle, the mold carriage 1 is at the extreme upper end of the inclined bed 2. Hydraulic by-pass valve 27 is open to permit rapid movement of the mold carriage up and downthe inclined bed. The mold carriage is retracted to the lower end of the inclined bed to the bell core setting position. The mold is preferably coated, during this retraction, with a slurryof refractory, insulating material in accordance with the invention disclosed and claimed in the Schuh et al. Patent No. 2,399,602 by means of spray nozzles, not shown; the spout end 17 of trough 6. The bell core 10 is set in place and the machine is now ready for casting. Since the machine is at thelower end of the inclinedubed, the operator throws the manual machine operating lever 24 to the proper position to move the mold carriage to the extreme upper end of the inclined bed.

As the mold carriage 1 moves up the inclined bed2, shoe 12 on the side of the mold carriage trips first limit' switch 13 actuating first timer 36 which energizes both the photoelectric cell shutter circuit 37 and the ladle drive circuit 38. The shutter 19 whichshields the photoelectric cell to prevent untimely triggering of the second' timer 39 is lifted from in front of the photoelectric cell, and the ladle 3 starts to tilt and pour. When. the machine reaches the position shown in Figure 1 the operator closes the hydraulic by-pass valve 27 so that the rate of carriage movement is controlled by adjustable valve 29 that has been set to give proper casting speed, and the. mold is brought up to centrifugal speed. By this time. molten metal is running down the trough 6sas a resultof' tilting of the ladle 3. When this molten metal reaches the spout end 17 of the trough, the photoelectric cell16 being focused at that point detects the molten metal and sends a weak signal to the amplifier 18 which provides amplified signal to the solenoid operated 3-way pilot valve 20 in the pneumatic circuit. The piston in pneumatic cylinder 23 moves with the result that the 4-way operating valve 25 is moved to casting position and the mold carriage starts to retract from the pouring trough.

At the same time second timer 39 is actuated, and as the mold carriage moves down the inclined bed, the time on first timer 36 expires, but the ladle drive circuit 38. remains operative since the second timer 39 is connected in parallel with the first timer 36. Whenthe first timer runs out, the shutter 19 drops over the photoelectric cell due to the de-energizing of the shutter circuit 37.

When the mold carriage l reaches the positionshown switch 14 actuates timer 33 (see Figure 5) providing power to 4-way solenoid operated air pilot valve32 which in turn controls air operated hydraulic valve 30 in the" hyd aulic system. When the solenoid of pilot valve 32 is energized, hydraulic valve 30 is closed so that all the fluid passing through the hydraulic system passes through needle valve 31 which has been adjusted in advance to give the desired mold carriage speed during hand-checking. At the expiration of the time set on timer 33, power to solenoid operated pilot valve 32 is cut off and air operated hydraulic valve 30 automatically opens. The fluid flow in the hydraulic system is again controlled by adjustable valve 29, and the mold carriage actuated by hydraulic cylinder 28 resumes normal casting speed until the stroke is completed. As the mold carriage 1 approaches the spout end 17 of the trough, the time set on second timer 39 elapses and power to the ladle drive circuit '38 is cut oil and the ladle stops tilting and drops back to its original position thus cutting off pouring after a preset time. Since the rate of movement of the mold carriage is precise, ladle cut back will occur during hand checking. After the mold carriage clears the spout end of the trough, it comes to a stop in the position shown in Figure 3. By-pass valve 27 in the hydraulic system is now opened by the operator and mold rotation is stopped as soon as the metal has solidified. The mold carriage is then bumped against bumping block 15 to break the pipe loose from the mold wall if required, and the pipe is extracted by holding the pipe stationary and moving the mold carriage up the inclined bed, and the machine is now ready to go through another cycle.

The valves and timers which are necessary only to the casting stroke do not operate during the extraction and mold coating strokes, so it is necessary for the operator to press a reset button to activate these circuits after the coating stroke is completed. It is necessary to wire these circuits in this manner to prevent ladle dumping and to permit rapid mold carriage movement during these operations.

It will be understood, of course, it is not intended that the invention be limited to the particular embodiments described above or shown in the drawings which have been set forth merely by way of example. The photoelectric cell could be replaced with any other means, either electrical or mechanical, capable of detecting the flow of molten metal and providing a reliable signal to initiate withdrawal of the casting machine. In the embodiment shown and described, the amplifier is utilized to assure a signal of intensity capable of triggering the various circuits; however, if the detection device used provides enough power to do this then the amplifier need not be used. In addition the hand-checking operation can be varied considerably with the same result. For example, instead of holding ladle dump constant while reducing mold carriage speed, the same results could be obtained by increasing ladle dump and holding mold carriage speed constant. Also, mold carriage slow down and ladle dump increase could be combined, and of course, mold carriage slow down also includes complete stopping of the mold carriage.

In order to realize the full benefits of the casting method of this invention, it is necessary that the ladle dump and mold carriage speed be capable of substantially constant rates both during a single cycle and from one cycle to another. Of course, the particular timer settings will vary from machine to machine, and the proper settings can easily be determined by simple experimentation with the machine being used. Thus it is obvious that through the elimination of human judgment it is possible to obtain from any given machine the maximum quality in pipe which it is capable of producing.

I claim:

1. In a centrifugal pipe casting machine having a pouring trough and a mold rotatably mounted on a carriage reciprocable with respect to said trough, the mold surrounding the trough into which molten metal is poured from a ladle and being retracted therefrom during reciprocation of the carriage, in combination therewith, a first limit switch positioned to 'be tripped by the mold carriage as it moves over the pouring trough, ladle tilting means responsive to the closing of said first limit switch, a photoelectric cell aimed at the spout end of the pouring trough for detection of molten metal pouring therefrom, means responsive to the signal from the photoelectric cell for starting retraction of the mold from the pouring trough, a ladle reverse mechanism controlled by a timer actuated by the signal from the photoelectric cell, a second limit switch positioned to be tripped by the mold carriage at a predetermined position near the end of the retraction step, retraction slow down means adapted to operate in response to the second limit switch and controlled by a timer which is actuated by said second limit switch and which is adjusted to maintain retraction slow down for a predetermined time.

2. In a centrifugal pipe casting machine having a pouring trough and a mold rotatably mounted on a carriage reciprocable with respect to said pouring trough, the mold surrounding the trough into which molten metal is poured and being retracted therefrom during reciprocation of the carriage, in combination therewith, a photoelectric cell aimed at the spout end of the pouring trough for detection of molten metal pouring therefrom and means responsive to the signal from the [photoelectric cell for starting retraction of the mold from. the pouring trough, a ladle reverse mechanism controlled by a timer actuated by the signal from the photoelectric cell, a limit switch positioned to be tripped by the mold carriage at a predetermined position near the end of mold retraction, retraction slow down means adapted to operate in response to the limit switch and controlled by a timer which is actuated by said limit switch and which is preset to maintain retraction slow down for a predetermined time.

3. In a centrifugal pipe casting machine having a pouring trough and a mold rotatably mounted on a carriage reciprocable with respect to said trough, the mold surrounding the trough into which molten metal is poured and being retracted therefrom during reciprocation of the carriage, in combination therewith, a photoelectric cell aimed at the spout end of the pouring trough for detection of molten metal pouring therefrom and means responsive to the signal from the photoelectric cell for starting retraction of the mold from the pouring trough comprising a solenoid operated air valve and a pneumatic cylinder adapted to operate the carriage control mechanism, a limit switch positioned to be tripped at a pre determined position near the end of mold retraction and a timer which is energized by said limit switch and which actuates and controls for a preset time the retraction slow down means comprising a solenoid operated air pilot valve connected in circuit with an air operated hydraulic valve in the mold carriage hydraulic system.

4. In a centrifugal pipe casting machine having a pouring trough and a mold rotatably mounted on a carriage which may be moved up and down an inclined bed with respect to said trough so that the mold surrounds the trough into which molten metal is poured when the carriage is moved up the inclined bed and is retracted from said trough when said carriage is moved down the inclined bed, in combination therewith, a limit switch positioned to be tripped at a predetermined position near the end of mold retraction, a timer connected so as to be energized by said limit switch, a solenoid operated air pilot valve actuated by said timer, and an air operated hydraulic valve which controls the flow of fluid in the mold carriage hydraulic system and which closes and opens in response to said air pilot valve, the closing of said hydraulic valve reduces the fluid flow in the mold carriage system with the result that the retraction speed is reduced for the time set on the timer.

References Cited in the file of this patent UNITED STATES PATENTS 

